Poor, skinny hens

I have 15 Buff Orpingtons and 4 Reds in a large pen. They are fed Lone Star laying Pellets as well as a grain "chicken Scratch". All of them are very poor looking. They get plenty of feed, and fresh water, but they have eaten most of the grass from their pen. I have given them Wazine in the past, but it's been about 2 months since their last dose.

Am I missing something that I should be feeding them? We are only picking up 3 to 4 eggs a day. We were picking up about 10 per day several weeks ago. Not only would I like to get more eggs, but I don't like my chickens being skinny. PLEASE HELP !!!